Smoker in our Building

There is a smoker in the apartment building where we live. If I had known that before we signed the lease, we wouldn't have rented here, but now we're stuck for a while. Does anyone have advice for keeping their smoke out of our apartment and away from our babies? I was thinking of a HEPA air cleaner? Fortunately we won't be here for long, but I'm concerned that the smoke is already causing some breathing issues.

We have a smoker next door Ughhh she drives us nuts! Some days the smell is so strong in the rooms where we share a wall. We complained to the landlord, but they didn't do anything because people are allowed to smoke in the apartments (which is crazy!!). I told her pulmonologist about it and she said the HEPA filters may help some. We have two in our 600 sq. ft. apartment. She also said to not keep her in the rooms too long where we share a wall. I can't wait to move!!